“I’ve heard this term used before but I am not sure what it means: ‘Slain in the Spirit.’ Does the Bible say anything about this?”— Billie

This term is typically used to describe a religious experience in which a person falls down or passes out presumably as a result of being “overcome” by the Spirit of God. The concept is not clearly biblical; indeed, the particular phrase does not appear to be found in Scripture. It is possibly derived from a few passages wherein individuals confronted with supernatural entities “fall down as dead” or “fall on (their) face” (Rev. 1:17; Ezek. 1:28; 44:4; Dan. 8:17-18; 10:7-15).
We cannot make an argument for or against the validity of this experience. The Spirit certainly may do what the Spirit chooses to do (I Cor. 12:4ff). Based purely on biblical content, however, we can say the event, as a work of God’s Spirit is rare if it happens at all.
Perhaps a more useful approach is to focus on what the Scripture says the Spirit does. The Bible teaches that the Holy Spirit has much to do with newness of life and change for the better. The Spirit makes one truly alive (Rom. 8:11), adopts believers into God’s family (Rom. 8:15-16), helps our infirmities and prays on our behalf (Rom. 8:26-27).
The Spirit gives gifts for service (I Cor. 12) and grows Christian character (Gal. 5:22-23). In the Spirit, a believer finds freedom (II Cor. 3:17) while also being convicted of wrong and assured of the reality of judgment (Jn. 16:7-11). The Spirit offers comfort to the soul (Jn. 14:16ff) and brings to our mind the truths Christ taught.
Are you looking for a life-changing, hope-giving experience in your life? Rather than seeking to be slain in the Spirit, you may want to explore being “born again” (Jn. 3:1-8).